Differences in energy metabolism between normal weight ‘large-eating’ and ‘small-eating’ women

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Abstract
Nine ‘large-eating’ (approximately 12 MJ/d) and nine ‘small-eating’ (approximately 5.3 MJ/d) women were selected from the population on the basis of diet and activity diaries. At rest and in the post-absorptive state the rate of oxygen consumption (Vo2)/kg fat-free mass (FFM) and rate of carbon dioxide production (Vco2)/kg FFM were 9–17% higher (P < 0.05) in the ‘large-eaters’ than in the ‘small-eaters’. As energy expenditure was increased by walking at 2.4, 3.9 and 5.4 km/h the differences between the two experimental groups for bothVo2/kg FFM andVco2/kg FFM were decreased to negligible values, but energy expended on a body-weight basis (MJ/kg per min) remained significantly higher (5–10%) in ‘large-eaters’. Oral temperature was also consistently higher (up to 0.5°) in this group both at rest and during sitting, standing and walking activities. Although the average thermic effect of a standardized liquid meal tended to be higher (27%; not significant) in the ‘small-eaters’, the other results demonstrate that the ‘large-eating’ females had a markedly higher rate of energy expenditure at rest and during light physical activities.